Method for converting hydrocarbons



April 27, 1937y .1. s. HARRISON 2,078,493

METHOD FOR CONVERTING HYDROCARBONS Filed Dec. 2, 193C ATToRNEYs,

Patented Apr. 27, 1937 UNITED STATES PATENT OFFICE METHOD FOR CONVERTINGHYDRO*- CARBON S Application December 2, 1930, Serial No. 499,507

8 Claims.

In the production of motor fuel by cracking petroleum, it has beencustomary to heat the raw material, generally a gas oil fraction, underliquid-phase conditions, and finally distill from 5 the products adesired motor fuel fraction. Some effort also has been made to crack inVaporphase, by heating vaporized hydrocarbons at a comparatively hightemperature range. Each of these offer some advantages, but accompanied0 by limitations in general. I have now found, however, that limitationsas encountered in these respective systems may be obviated, and withunexpected advantages and results generally. The invention, then,comprises the features hereinafter fully described and particularlypointed out in the claims, the following description and the annexeddrawing setting forth in detail certain illustrative embodiments of theinvention, these being indicative, however, of but a few of the variousWays in which the principle of the invention may be employed. l In saidannexed drawing:\

The sole ligure is a semi-diagrammatic elevation of apparatuscontemplated in the invention.

Jliteferring more particularly to the drawing, there is shown a heatingmeans, which involves an initial heater 2, most advantageously forinstance in the form of a so-called coilor bank of connectedtubes, andexposed to products of co-mbustion of a suitable furnace 3, or at leastsuch vas to be out of the hottest portion, so as to receive an initialheating not too abruptly. From this, a further or main heater 4advantageously .35 of so-called coil type, connects with the heater 24and is located in the hotter or radiant portion of y `the furnacechamber. From the heater 4, a con- ,nection 5 leads to a liquid-phasedigester tank or drum 6, guarded against heat-loss, as by an insulatingjacket or a flue-gas jacket, and prefer-` ably in vertical position.From this in turn a `connection I proceeds to a lower-pressure drum 8.apressure regulating valve 9 being interposed Vin the line. Connectedwith the drum 8 isa distillation or fractionating tower I0, the detailof which may vary, but which may contain bafes or plates, preferablysuch as to provide a bubbling of vapors through a liquid layer. In theconnection II enroute from the drum 8, partial condensers I2, I3, I4 aredesirably introduced, these being of any convenient constructionfacilitating the'passage of the hot vapors from the drum l,throughpassways such as to be in heat exchange relation with the feed line I5.The latter con- .5 5 nects to the heating coil 2, and proceeds from apump I6 and drum II having further connections, among which is an inputline I8 connectin-g through partial condensers I9, 20, 2I and thence toa vfeed pump 22 supplied from any suitable source of raw-material. Afurther distillation or fractionating tower 23 desirably is arranged,having an input line 24 proceeding from the partial condensers I9, 20,in which heat exchange is had with the feed line I8. From the tower I0 adrain line 25 leads to drum I'I, and a similar drain line 26 is providedfor tower 23. A connection 2l in continuation extends to a heater 28,which again preferably is of so-called coil type, and placed in. aposition to receive heat, but vnot the more direct heat of the furnace.Preferably, such heater may be positioned in the same setting 3 alreadyreferred to, and in the portion thereof leading to the stack olf-take29. From the heater 28, a connection leads to a further main heater 30',which may be included in the same furnace setting 3 before referred to.Such heater then in turn connects with a heater section 3| which againmay be positioned in its own controlled furnace, or preferably may belikewise provided in the same setting aforesaid, such heater being inthe high temperature or radiant portion thereof, and again for instancebeing of soi-called coil type. From this, a connection 32 leads to drum8.

In the practice of the process, the desired raw material, for example agas oil fraction, is forwarded from a suitable source of supply throughpump-line 22 and heat exchangers 2|, 20, I9 and connection I8 to drumI'I. From this, material is forwarded by pump I6 to heat exchangers I3,I2, (valve bbeing opened, and valves b" and b" being closed for thispurpose) and through line I5 to the coil 2, Where the oil is preheated,and is then forwarded to the main heating coil Il, and thence throughline 5 to drum 6. The conditions in the heating coil portion of the.system and the digester drum 6 are such as Ato maintain liquid-phasecracking, the pressure on the drum as determined by valve 9 being on theorder of 400-1200 pounds per square inch,'for instance, and thetemperature in the neighborhood of, but not exceeding 975 F. Preferably,a pressure of about 1,000 pounds per square inch and a temperature ofabout 925 F. as maximum from the heating coil, is provided. Lowerpressure prevails in the drum 8, such pressure being less than 200pounds per square inch, and preferably on the order of about 100 pounds.Atthe same time, material is being supplied to coil 30. The material forthis portion of the system may be forwarded from a suitable source ofsupply by pump 33 through heat exchanger l4, (valves b" bi being closedfor such alignment), and valve 34 being open and valve 35 being closed.The material then proceeds through preheating coil 28, main heatersections 3i, and thence through connection 32 to drum 8 to mingle inheated state with the material entering at the same time from theliquidphase portion of the system. Conditions in the portion 35, 3l ofthe system are maintained for vapor-phase cracking, the temperaturebeing above 1,000 F., and the pressure not exceeding 200 pounds persquare inch. Preferably, a temperature of 1025-1125 F. is maintained forthe maximum as leaving coil 3 I. As material supplied by pump line S3,any desired petroleum distillate may be employed. Advantageously, aheavy naphtha may be used, for instance a heavy crude naphtha. From thedrum 8, vapors proceed through line ll to the heat exchangers I2, i3, i4acting as partial condensers, the operation being controlled by theamount of cooler oil shunted therethrough by the control valves u.Condensate from the partial condensers is taken off by connections 36,3l, and may be returned to desired points of the system, or may beotherwise disposed of as preferred. A drain line 38 from the drum 8provides for removal of accumulating unvaporized material. From theexchanger I4, the vapors proceed to tower l0, where distillation andfractionation occurs, the uncondensed vapors proceeding from the top ofthe tower to partial condensers i9, 20, and the unvaporized ends aredischarged by the connection 25 to drum Il to mingle with the incomingfeed, and recycle as desired. From the partial condenser 20, theremaining vapors proceed through connection 24 to tower 23, wheredistillation and fractionation proceeds, the remaining vapors passing byconnection 39 from the top of the tower to partial condenser 2|, andthence to final condenser 40 and receiver 4 l. The unvaporizedaccumulation in the bottom of tower 23 is taken off through connection26, and with valve 42 open and Valves 35 and 44 closed, proceeds throughcooler 45 to receiver 46. Receivers 4i and 45 may be provided withdrawoff connections 4l, 48 and gas connections 49, 50. By opening Valve44, and closing valves 42 and the products from tower 23 may be directedinto drum il for recycling if desired.

With advantage, the material fed through the vapor-phase crackingportion of the system may be a heavy cracked distillate as obtained inthe fractionating portion of the system itself. For this, valves 42, 44may be closed, and valve 35 may be opened, and valve 34 further beingclosed, pump 5! may then forward the heavy cracked distillate from thefractionating portion of the system itself into, the Vapor-phase coilsystem 28, 30, 3l. Heat exchanger I4 will at this time be cut back intothe line l5, the valves bi', bi being opened and valve b being closed.The procedure otherwise is as described.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of' the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A process of altering the boiling point of hydrocarbons, whichcomprises heating a petroleum distillate under pressure, then digestingin a Zone guarded against substantial heat-loss and being withouttemperature-rise from external heat and providing liquid-phase crackingconditions, releasing the material into a zone of lower pressure,heating another petroleum distillate at a higher temperature but lowerpressure providing substantially vapor-phase cracking conditions, andindependently discharging into admixture in the same lower pressureYZone aforesaid.

2. A process of altering the boiling point of hydrocarbons, whichcomprises heating a petroleum fraction at not exceeding 975 F., thendigesting in a zone guarded against substantial heat-loss and beingwithout temperature-rise from external heat and providing liquid-phasecracking conditions under a pressure of G-1200 pounds per square inch,releasing the material into a zone of lower pressure not exceeding 200pounds, heating another petroleum distillate: at a temperature of1025-1125o F. at pressure not exceeding 200 pounds per square inchproviding substantially vapor-phase cracking conditions, andindependently discharging into admixture in the same lower pressure Zoneaforesaid.

3. A process of altering the boiling point of hydrocarbons, whichcomprises heating a petroleum fraction at not exceeding 925 F., then`digesting in a zone guarded against substantial heat-loss and beingwithout temperature-rise from external heat and providing liquid-phasecracking conditions under a pressure of about 1000 pounds per squareinch, releasing the materail into a zone of lower pressure, heatinganother petroleum distillate at a temperature of 1025- 1125o F. atpressure not exceeding 200 pounds per square inch providingsubstantially Vapor-phase cracking conditions, and independentlydischarging into admixture in the same lower pressure Zone aforesaid.

4. A process of altering the boiling point of hydrocarbons, whichcomprises heating a petroleum distillate, then digesting in a zoneguarded against substantial heat-loss and being without temperature-risefrom external heat and under pressure producing liquid-phase crackingconditions, releasing the material into a zone of lower pressure,separately heating another petroleum distillate at a higher temperatureand lower pressure under substantially Vapor-phase cracking conditions,and discharging such vapor-phase output into the aforesaidlower-pressure zone.

5. A process of altering the boiling point of hydrocarbons, whichcomprises heating a petroleum distillate, then digesting in a zoneguarded against substantial heat-loss and being without temperature risefrom external heat and under pressure providing liquid-phase crackingconditions, releasing the material into a zone of lowen pressure,separately heating a lighter distillate at a higher temperature andlower pressure under substantially vapor-phase cracking conditions, anddischarging such vapor-phase output into admixture in the aforesaidlower-pressure zone.

6. A process of altering the boiling point of hydrocarbons, whichcomprises heating a petroleum distillate, then digesting in a zoneguarded against substantial heat-loss and being without temperature-risefrom external heat and under pressure producing liquid-phasev crackingconditions, releasing the material into a zone of lower pressure,separately heating another petroleum distillate at a higher temperatureand lower pressure under substantially vapor-phase cracking conditions,discharging such vapor-phase output into admixture in the aforesaidlower-pressure zone, distilling from the products a motor fuel,

and returning heavy ends therefrom as the aforementioned secondpetroleum distillate.

7. A process of altering the boiling point of hydrocarbons, whichcomprises passing a stream of a petroleum distillate through a heatingzone under high pressure into the lower part of a digester zoneproviding a time period of reaction under liquid-phase crackingconditions, simultaneously passing another stream of a petroleumdistillate 10 through a vapor phase heating zone under a highertemperature and lower pressure than that first mentioned, anddischarging the stream from said latter heating zone and the stream fromthe upper portion of said digesting zone together into 15 2, lOWeI'pressure ZODB.

8. A process of altering the boiling point of hydrocarbons, whichcomprises passing a stream of a petroleum distillate through a heatingzone under high pressure providing liquid-phase cracking conditions andthence into the lower portion of a digesting zone, whereby to reduce thevelocity of the stream and provide a time period of reactionsimultaneously passing another stream of a petroleum distillate througha. vapor phase heating zone under a higher temperature and lowerpressure than the aforementioned, discharging products from said latterheating zone and from the upper portion of said digesting zone into alower pressure zone, fractionating vapors from said lower pressure zone,and supplying a heavy distillate therefrom as the aforementioned secondstream of distillate.

JOHN STEWART HARRISON.

